Abstract

The usage of antimicrobial drugs, such as antibiotics, as growth enhancer in
livestock farming is prohibited in many countries. In recent years, antimicrobial
resistance associated with the use of antimicrobial drugs in animals has triggered
vast public attention. Thus, recent approach to enhance the growth performance of
livestock is through supplementation of probiotic and digestive enzymes. Probiotic
are live microorganisms, when consumed in adequate amounts will confer health
benefit on the host.
Generally recognised as safe status of lactic acid bacteria (LAB) and the increasing
demand of probiotic in food and feed industry have driven current attempt to
determine the probiotic potential of six bacteriocinogenic Lactobacillus plantarum
strains (UL4, TL1, RS5, RI11, RG11 and RG14) isolated from Malaysian foods,
through in vitro probiotic characterisation study and in vivo animal trials. In the in vitro study, the antimicrobial potential of Lb. plantarum strains and
bacteriocins was carried out, followed by the study to assess the ability of these
strains to overcome simulated gastric and small intestinal tracts, deconjugate bile
salts (sodium taurocholate, sodium glycocholate, sodium taurodeoxycholate and
sodium glycodeoxycholate), assimilate cholesterol and adhere to intestinal epithelial
Caco-2 cell line. In vivo animal trials were then carried out to evaluate the
effectiveness of Lb. plantarum strains and bacteriocins produced on growth
performance, intestinal microflora and histomorphological changes, and alteration of
short chain fatty acids and serum cholesterol level of rats.
In the in vitro study, Lb. plantarum strains and their bacteriocins had exhibited
strong bacteriocidal and bacteriostatic antimicrobial action against Gram-positive
and –negative bacteria. Lb. plantarum strains had strongly inhibited the growth of
Bacillus cereus B43 and Listeria monocytogenes L55, whereas bacteriocins had
inhibited the Pediococcus acidilactici 4-46, Enterococcus faecalis N-103,
Enterococcus faecium ATCC 19434, Listeria monocytogenes L55, Bacillus cereus
B43, Streptococcus pneumoniae S972 and Staphylococcus aureus S942. Lb.
plantarum strains were highly tolerance to the exposure of simulated gastric and
small intestinal juices. They were able to deconjugate bile salts and assimilated 56.7
– 100.0% of cholesterol. Lb. plantarum strains adhered strongly to the Caco-2
epithelial cell line and reduced the adherence of L. monocytogenes L55 substantially.